1. Field of the Invention
The invention relates to a BCA data reproduction method and apparatus for optical discs, in which a defect signal generated from a defect detector in a signal reproduction unit is used as a BCA (Burst Cutting Area) signal.
2. Description of the Related Art
Typically, digital video discs or digital versatile discs (hereinafter referred to as DVDs) include DVD-ROM (Read Only Memory), DVD-R (Recordable), and DVD-RAM (Random Access Memory). In the development of DVD-ROM disk, it has been suggested to provide a BCA (Burst Cutting Area) for the purpose of providing information for identifying each of the DVD-ROM discs. A BCA code (signal) is recorded on the aforementioned DVD-ROM disc, after a predetermined video data or the like is recorded, by partially removing with a laser beam an aluminum film which has been deposited as a reflection film. That is, a BCA code is formed by removing an aluminum film of an area not affecting reproduction of a video data, audio data, or computer data which has been recorded as a pit signal on the disc. More specifically, the BCA code is recorded so as to be overwritten on a pit string of dummy data recorded on an area located along the inner circumference of the disc.
As shown in FIG. 1, the BCA 11 is recorded as bar-code stripes in the circumferential direction of the optical disc 10, and each stripe has a length of about 1 mm between 22.3 (+0/−0.4) mm to 23.50±0.5 mm from the center of the center hole of the disc. The BCA data writing method adopts a laser beam to remove a part of the area of the reflection film in a radiation direction. In general, the BCA data is recorded by way of a RZ (return to zero) modulation method and read out by an optical pickup serving for reproducing video data or audio data recorded on the optical disk. Since a dummy pit string has already existed in the original BCA, when the optical pickup head reads the BCA data, the obtained RF (radio frequency) signal includes a BCA stripe signal and a high-frequency pit string signal. FIG. 2 shows the RF signal and the BCA signal for the BCA, wherein FIG. 2(A) shows the RF signal and FIG. 2(B) shows the BCA signal.
FIG. 3 is a block diagram showing a conventional BCA signal reproduction apparatus. In the conventional BCA signal reproduction method, a BCA signal reproduction apparatus is used to extract the desired BCA information from the RF signal. As shown in FIG. 3, the BCA signal reproduction apparatus utilizes a peak detector 31 to detect the peak value of the RF signal. Since the RF signal carries the high-frequency pit signal, a low-pass filter (LPF) 32 has to be used to filter out the high-frequency component in the RF signal. Furthermore, a slice signal generator 33 is utilized to generate a slice signal corresponding to the RF signal. Then, two processed signals are compared in a comparator 34, which generates a BCA signal accordingly. However, since the RF signal is subjected to BCA's mirror modulation, thus causing the phenomenon of DC wandering, and the high-frequency component in the RF signal may not be completely filtered out easily, a correct BCA signal cannot be extracted in the conventional method.
Further scope of the applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.